Disaggregation of Sales, Geographic Sales and Product Sales - Net Sales by Geographic Areas (Details) - USD ($) $ in Thousands		3 Months Ended
		Apr. 03, 2020	Mar. 29, 2019
Geographic And Sales [Line Items]
Total net sales		$ 35,187	$ 32,583
Geographic Distribution, Domestic [Member]
Geographic And Sales [Line Items]
Total net sales		1,739	1,952
Geographic Distribution, Foreign [Member]
Geographic And Sales [Line Items]
Total net sales		33,448	30,631
Geographic Distribution, Foreign [Member] | China [Member]
Geographic And Sales [Line Items]
Total net sales		11,715	11,771
Geographic Distribution, Foreign [Member] | JAPAN
Geographic And Sales [Line Items]
Total net sales		8,302	5,519
Geographic Distribution, Foreign [Member] | Other [Member]
Geographic And Sales [Line Items]
Total net sales	[1]	$ 13,431	$ 13,341

[1] No other location individually exceeds 10% of the total sales.